The invention relates to a measuring device with a test tape cassette for measuring the torque occurring on the hubs of the two tape spools.
Test tape cassettes are known, whose tape spools comprise a hub and a spool body, which are rotatably reciprocally mounted by means of a ball bearing collar and a spring element acts between the hub and the spool body. If the hub is now driven by the driving cam of a tape recorder, the torque acting on the hub rotates the latter with respect to the outer spool body and thereby tensions the spring element. The angular displacement between hub and spool body brings about a corresponding tensioning of the spring element, so that the angular displacement is a measure of the torque acting on the hub. In the case of the known test tape cassettes, the tape spools carry a scale on which the acting torque can be read off a marking system as a function of the angular displacement between the hub and the spool body. Therefore the scale is in joules and not in radians.
Such test tape cassettes are used for determining the torque, which is transmitted by the slip clutch of the driving cam. In order to achieve uniform tape running, the slip clutch should cause no torque fluctuations. Therefore the slip clutch quality can be checked by a continuous torque measurement. In the case of conventional test tape cassettes, it is not possible to determine the torque in closed tape recorders, e.g. in the cassette part of car radio or other built-in equipment, because the torque must be directly read off the top of the test tape cassette. Therefore it is scarcely possible to observe torque fluctuations with this visual measurement system.